1. Field of the Invention
The present invention relates to a method for transmitting and receiving signals using multi-band Radio Frequencies (RFs) to improve reliability and/or throughput of a communication system that supports multi-band RFs.
2. Discussion of the Related Art
The following description is given mainly focusing on a downlink (DL) mode in which a base station transmits signals to one or more terminals. However, it will be easily understood that the principle of the present invention described below can be directly applied to an uplink (UL) mode simply by reversing the procedure of the DL mode.
A technology in which one MAC entity manages multiple carriers (or frequency allocation bands (or simply “frequency allocations (FAs)”)) has been suggested to efficiently use multiple bands or multiple carriers.
FIGS. 1A and 1B schematically illustrate a method for transmitting and receiving signals using multi-band RFs.
In FIGS. 1A and 1B, PHY0, PHY1, . . . PHY n-2, and PHY n-1 represent multiple bands according to this technology and each of the bands may have a Frequency Allocation (FA) size allocated for a specific service according to a predetermined frequency policy. For example, the band PHY0 (RF carrier 0) may have a band size allocated for a general FM radio broadcast and the band PHY1 (RF carrier 1) may have a band size allocated for mobile phone communication. Although each frequency band may have a different band size depending on the characteristics of the frequency band, it is assumed in the following description that each Frequency Allocation band (FA) has a size of A MHz for ease of explanation. Each FA can be represented by a carrier frequency that enables a baseband signal to be used in each frequency band. Thus, in the following description, each frequency allocation band will be referred to as a “carrier frequency band” or will simply be referred to as a “carrier” as it may represent the carrier frequency band unless such use causes confusion. As in the recent 3GPP LTE-A, the carrier is also referred to as a “component carrier” for discriminating it from a subcarrier used in the multicarrier system.
From this aspect, the “multi-band” scheme can also be referred to as a “multicarrier” scheme or “carrier aggregation” scheme.
In order to transmit signals through multiple bands as shown in FIG. 1A and to receive signals through multiple bands as shown in FIG. 1B, both the transmitter and the receiver need to include an RF module for transmitting and receiving signals through multiple bands. In FIGS. 1A and 1B, the method of configuring a “MAC” is determined by the base station, regardless of the DL or UL mode.
Simply stated, the multi-band scheme is a technology in which one MAC entity, which will simply be referred to as a “MAC” unless such use causes confusion, manages and operates a plurality of RF carriers to transmit and receive signals. RF carriers managed by one MAC do not need to be contiguous. Accordingly, this technology has an advantage of high flexibility in management of resources.
For example, frequencies may be used in the following manner.
FIG. 2 illustrates an example wherein frequencies are allocated in a multi-band-based communication scheme.
In FIG. 2, bands FA0 to FA7 can be managed based on RF carriers RF0 to RF7. In the example of FIG. 2, it is assumed that the bands FA0, FA2, FA3, FA6, and FA7 have already been allocated to specific existing communication services. It is also assumed that RF1 (FA1), RF4 (FA4), and RF5 (FA5) can be efficiently managed by one MAC (MAC #5). Here, since the RF carriers managed by the MAC need not be contiguous as described above, it is possible to more efficiently manage frequency resources.
In the case of downlink, the concept of the multi-band-based scheme or carrier-aggregation-based scheme described above can be exemplified by the following base station/terminal scenario.
FIG. 3 illustrates an example scenario in which one base station communicates with a plurality of terminals (UEs or MSs) in a multi-band-based scheme.
In FIG. 3, it is assumed that terminals 0, 1, and 2 have been multiplexed. The base station 0 transmits signals through frequency bands managed by carriers RF0 and RF1. It is also assumed that the terminal 0 is capable of receiving only the carrier RF0, the terminal 1 is capable of receiving both the carriers RF0 and RF1, and the terminal 0 is capable of receiving all the carriers RF0, RF1, and RF2.
Here, the terminal 2 receives signals of only the carriers RF0 and RF1 since the base station transmits only the carriers RF0 and RF1.
However, the above multi-band-based communication scheme has only been conceptually defined and can be regarded simply as a scheme in which an additional frequency allocation band (FA) is allocated when needed. Thus, there is a need to define, in more detail, a signal transmission/reception scheme or a multiplexing method that enables high-efficient and high-performance processing.
In addition, there is a need to study a technology for more efficiently improving reception performance when an HARQ scheme is applied to the multi-band-based communication scheme.
Since channel coding or multiplexing is generally performed for each frequency band in the above technology, the diversity or multiplexing gain may be limited.